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https://issues.apache.org/jira/browse/DERBY-5680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13695629#comment-13695629
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ASF subversion and git services commented on DERBY-5680:
--------------------------------------------------------

Commit 1497868 from [~mamtas]
[ https://svn.apache.org/r1497868 ]

DERBY-5680( indexStat daemon processing tables over and over even when there 
are no changes in the tables )

Backporting the 3 commits that went in for DERBY-5680 to 10.8. The 3 commits 
were 1340549, 1341622, 1341629. The first two commits were easy to backport 
using svn merge command but the third commit 1341629 ran into conflicts. For 
that backport, hand made the changes since there were not too many changes.

The changes for this jira has added a new property 
derby.storage.indexStats.debug.keepDisposableStats. The intention of the 
property is that if the property is set to true, we do not delete the 
orphaned/disposable stats. If the property is set to false, the 
orphaned/disposable stats will get dropped by the index stats daemon. Currently 
known reasons for orphaned/disposable stats are
1)DERBY-5681(When a foreign key constraint on a table is dropped, the 
associated statistics row for the conglomerate is not removed). Fix for this 
has been backported all the way to 10.3
2)DERBY-3790(Investigate if request for update statistics can be skipped for 
certain kind of indexes, one instance may be unique indexes based on one 
column.) Fix for this is in 10.9 and higher

A junit test was added for this new property but it went in as part of 
DERBY-3790. The name of the junit test is 
store.KeepDisposableStatsPropertyTest. Had to make changes to this test to 
backport it to 10.8 but without the fix for DEBRY-3790 and with the absence of 
drop statistics procedure, the test really does not make much sense for 10.8 
codeline. The test uses drop statistics procedure and it is mainly testing 
DERBY-3790 to make sure that the orphaned stats are being deleted or left 
behind based on whether the property is set to true or false. But since we do 
not have drop statistics procedure and we do not have DERBY-3790 fixed in 10.8, 
we can't really meaningfully run the KeepDisposableStatsPropertyTest in 10.8. 
In any case, I have changed the test so that atleast it will not fail in 10.8 
but it is not able to truly test the property. May be we can test this property 
through upgrade suite where we will create orphaned stats because of DERBY-5681 
on older releases and we will find that when the property is set to true, even 
after upgrade, we will have orphaned stats but when property is set to false, 
after upgrade, orphaned stats are deleted.
                
> indexStat daemon processing tables over and over even when there are no 
> changes in the tables
> ---------------------------------------------------------------------------------------------
>
>                 Key: DERBY-5680
>                 URL: https://issues.apache.org/jira/browse/DERBY-5680
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.8.2.2, 10.9.1.0
>            Reporter: Brett Bergquist
>            Assignee: Kristian Waagan
>             Fix For: 10.9.1.0
>
>         Attachments: derby-5680-1a-drop_orphaned_stats.diff, 
> derby-5680-1b-remove_disposable_stats.diff, 
> derby-5680-2a-remove_redundant_check.diff, 
> derby-5680-3a-rename_debug_property.diff, 
> DERBY5680_backportTo108_patch1_diff.txt, 
> DERBY5680_backportTo108_patch1_stat.txt
>
>
> I think there is something wrong with the indexStats.     
> The problem happens on many tables in the database.   
> None of these tables are changing however, no inserts or deletes or updates.  
> They are being queried, however.  
> Here is one such table.
> Here is the statistics for this table:
> Table (Index)     2              3
> ACCOUNTTABLE_CONFIG_BUNDLE (SQL081029110443810)          numunique= 38390 
> numrows= 38390     2012-03-30 13:00:26.84
> ACCOUNTTABLE_CONFIG_BUNDLE (SQL100922215819290)          numunique= 38390 
> numrows= 38390     2012-03-30 13:00:26.917
> There are in fact 38390 rows in the table.
> Here is some of the indexStat trace:
> Fri Mar 30 12:47:12 EDT 2012 Thread[DRDAConnThread_43,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": update scheduled, 
> reason=[t-est=38390, i-est=2355 => cmp=2.7912562815443245] (queueSize=12)
> Fri Mar 30 12:47:48 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL081029110443810 (fc33890d-011d-491f-3d8c-0000376d74d3): rows=38390, 
> card=[38390]
> Fri Mar 30 12:47:48 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL100922215819290 (75608675-012b-3c38-b55c-000043ea6398): rows=38390, 
> card=[38390]
> Fri Mar 30 12:47:48 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": scan durations 
> (c30625=91ms,c30625=98ms)
> Fri Mar 30 12:47:48 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": generation complete (210 ms)
> Fri Mar 30 12:47:49 EDT 2012 Thread[DRDAConnThread_44,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": update scheduled, 
> reason=[t-est=38390, i-est=2355 => cmp=2.7912562815443245] (queueSize=19)
> Fri Mar 30 12:48:25 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL081029110443810 (fc33890d-011d-491f-3d8c-0000376d74d3): rows=38390, 
> card=[38390]
> Fri Mar 30 12:48:25 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL100922215819290 (75608675-012b-3c38-b55c-000043ea6398): rows=38390, 
> card=[38390]
> Fri Mar 30 12:48:25 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": scan durations 
> (c30625=93ms,c30625=95ms)
> Fri Mar 30 12:48:25 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": generation complete (211 ms)
> Fri Mar 30 12:48:25 EDT 2012 Thread[DRDAConnThread_50,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": update scheduled, 
> reason=[t-est=38390, i-est=2355 => cmp=2.7912562815443245] (queueSize=18)
> Fri Mar 30 12:48:57 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL081029110443810 (fc33890d-011d-491f-3d8c-0000376d74d3): rows=38390, 
> card=[38390]
> Fri Mar 30 12:48:57 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL100922215819290 (75608675-012b-3c38-b55c-000043ea6398): rows=38390, 
> card=[38390]
> Fri Mar 30 12:48:57 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": generation complete (243 ms)
> Fri Mar 30 12:49:27 EDT 2012 Thread[DRDAConnThread_56,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": update scheduled, 
> reason=[t-est=38390, i-est=2355 => cmp=2.7912562815443245] (queueSize=20)
> Fri Mar 30 12:49:36 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL081029110443810 (fc33890d-011d-491f-3d8c-0000376d74d3): rows=38390, 
> card=[38390]
> Fri Mar 30 12:49:37 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": wrote stats for index 
> SQL100922215819290 (75608675-012b-3c38-b55c-000043ea6398): rows=38390, 
> card=[38390]
> Fri Mar 30 12:49:37 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": scan durations 
> (c30625=111ms,c30625=108ms)
> Fri Mar 30 12:49:37 EDT 2012 Thread[index-stat-thread,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": generation complete (238 ms)
> Fri Mar 30 12:49:37 EDT 2012 Thread[DRDAConnThread_49,5,main] {istat} 
> "PKG_9145E_V1"."ACCOUNTTABLE_CONFIG_BUNDLE": update scheduled, 
> reason=[t-est=38390, i-est=2355 => cmp=2.7912562815443245] (queueSize=18)
> As can be seen, the "i-est" appears to be wrong and is used over and over 
> even though the statistics for the indexes have been updated.

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